PLASMONIC NANO-ALLOY PHOTOTHERMAL-COUPLED METHANE DRY REFORMING CATALYST, PREPARATION METHOD THEREFOR, AND APPLICATION THEREOF

Abstract

Disclosed are a plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst, a preparation method therefor, and application thereof, wherein the catalyst includes a ternary nano metal component and a magnesium-aluminum spinel, and can be used for directly converting greenhouse gases to fuel. The catalyst can absorb ultraviolet-visible light irradiated by an external xenon lamp in a photothermal reactor, and use thermal radiation to reach a temperature required for a thermal catalysis, thereby achieving higher solar-to-fuel conversion efficiency. Due to extremely high solar spectrum absorptivity, the catalyst has excellent performance, and is capable of using the visible light band to excite a plasmonic effect to pre-activate gas molecules 10 for the reaction, thereby reducing apparent activation energy under direct lighting, inhibiting the complete cracking of methane and avoiding the formation of carbon deposition, such that the stability of the methane dry reforming reaction and efficiency of the reaction are improved.

Claims

1. A plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst, wherein the catalyst is a catalyst NiCoZn/MgAlO.sub.x, in which the catalyst NiCoZn/MgAlO.sub.x uses a magnesium-aluminum spinel as a carrier, and nickel, cobalt and zinc as active metal components; and in a process of photothermal-driven methane dry reforming for hydrogen production, an addition of zinc promotes a high-energy hot electron injection induced by localized surface plasmon resonance, which activates a CH bond of CH.sub.4 and a CO bond of CO.sub.2 and inhibits complete cracking of CH.sub.4, thereby avoiding a formation of carbon deposition.

2. The plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst according to claim 1, wherein the active metal components account for 0.8%-10% of a mass of the carrier; and mass ratios of nickel, cobalt, and zinc in the catalyst NiCoZn/MgAlO.sub.x are 7%-8%, 0.01%-8%, and 0.01%-1%, respectively.

3. A preparation method for the plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst according to claim 1, comprising the following steps: (1) dissolving nickel salt, cobalt salt, zinc salt, magnesium salt, and aluminum salt in a solvent, and stirring to form a first solution; (2) adding a sodium hydroxide solution to the first solution to obtain a mixed solution, and continuing to stir vigorously; (3) performing a continuous hydrothermal reaction with the mixed solution stirred in the step (2) in a hydrothermal reactor; (4) performing centrifugation and washing to obtain a precipitate, drying and grinding the precipitate to obtain a NiCoZn alloy magnesium-aluminum spinel catalyst precursor; and (5) placing the NiCoZn alloy magnesium-aluminum spinel catalyst precursor in a tubular furnace under a mixed H.sub.2/N.sub.2 atmosphere, heating the NiCoZn alloy magnesium-aluminum spinel catalyst precursor to a desired temperature and keeping the desired temperature for a period of time to ensure sample reduction, and then cooling to room temperature to obtain the catalyst NiCoZn/MgAlO.sub.x.

4. The preparation method for the plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst according to claim 3, wherein in the step (1), a molar ratio of nickel salt, cobalt salt, zinc salt, magnesium salt, and aluminum salt falls within a range of 0-1:1:1:2:10.

5. The preparation method for the plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst according to claim 3, wherein in the step (3), a temperature of the continuous hydrothermal reaction is 120 C.-150 C., and the continuous hydrothermal reaction lasts for 45-50 hours.

6. The preparation method for the plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst according to claim 3, wherein in the step (5), a rate of the heating is 2 C./min, the desired temperature is 600 C., and the desired temperature is kept for 2 h.

7. Application of the plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst according to claim 1 in photothermal-driven methane dry reforming for hydrogen production.

8. The application of the plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst in photothermal-driven methane dry reforming for hydrogen production according to claim 7, wherein the application is performed in a photothermal reactor and comprises the following steps: (1) placing the catalyst NiCoZn/MgAlO.sub.x in a reaction crucible for a methane dry reforming reaction; (2) purging air in a pipeline of the photothermal reactor; (3) turning on a xenon lamp to irradiate with ultraviolet-visible light, simulating sunlight for focused lighting, with light spots directly irradiating a surface of the catalyst NiCoZn/MgAlO.sub.x; and (4) injecting high-energy hot electrons induced by localized surface plasmon resonance of the catalyst NiCoZn/MgAlO.sub.x under lighting, activating the CH bond of CH.sub.4 and the CO bond of CO.sub.2, inhibiting complete cracking of CH.sub.4 and avoiding a formation of carbon deposition.

9. The application of the plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst in photothermal-driven methane dry reforming for hydrogen production according to claim 8, wherein methane, carbon dioxide, and nitrogen gas are introduced to purge the photothermal reactor before the methane dry reforming reaction to replace impurities in the photothermal reactor.

10. The application of the plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst in photothermal-driven methane dry reforming for hydrogen production according to claim 8, wherein the focused lighting comes from the xenon lamp and precisely covers the surface of the catalyst NiCoZn/MgAlO.sub.x; and under the lighting, a plasmonic effect on the surface of the NiCoZn/MgAlO.sub.x catalyst promotes the methane dry reforming reaction, thereby achieving optimal photothermal coupled performance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a schematic diagram of hot electron excitation in a photothermal-driven methane dry reforming catalyst NiCoZn/MgAlO.sub.x.

[0024] FIG. 2 is a TEM electron microscope image of a photothermal-driven methane dry reforming catalyst NiCoZn/MgAlO.sub.x.

[0025] FIG. 3 is an XRD spectrum of a photothermal-driven methane dry reforming catalyst.

[0026] FIG. 4 is a comparison of comprehensive performance of a photothermal-driven methane dry reforming catalyst.

[0027] FIG. 5 is a comparison of a photothermal-coupled synthesis gas yield of a photothermal-driven methane dry reforming catalyst.

[0028] FIG. 6 is a stability diagram of a photothermal-driven methane dry reforming catalyst NiCoZn/MgAlO.sub.x.

[0029] FIG. 7 is an ultraviolet-visible-near-infrared spectrum absorption diagram of a photothermal-driven methane dry reforming catalyst.

[0030] FIG. 8 is a performance comparison of a photothermal-driven methane dry reforming catalyst under lighting of different light wavelengths.

[0031] FIG. 9 is a diagram showing main reaction energy barriers for methane dry reforming on different catalysts calculated by DFT.

[0032] FIG. 10 is a comparison of solar-to-fuel efficiency of methane dry reforming reaction for different ternary alloys.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The present disclosure will be further described below in conjunction with specific examples.

Example 1

[0034] A preparation method for a plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst, which is specifically prepared by the following method: [0035] (1) 0.582 g of nickel nitrate hexahydrate, 0.582 g of cobalt nitrate hexahydrate, 1.19 g of zinc nitrate hexahydrate, 1.023 g of magnesium nitrate hexahydrate, and 7.5 g of aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water, and stirred with a magnetic stirrer at room temperature for 30 min to form a first solution; [0036] (2) 50 mL of 1.68 mol/L sodium hydroxide solution was added to the mixed solution obtained in the step (1), then sonicated and stirred vigorously for 4 h; [0037] (3) the stirred solution in the step (2) was transferred into a polytetrafluoroethylene (PTEE)-lined container, which was then placed in a high-pressure reactor to react at 130 C. for 48 h; [0038] (4) the mixed solution obtained after hydrothermal treatment in the step (3) was centrifuged at 6000 r/min to obtain a precipitate, the precipitate was then washed five times with water and ethanol; [0039] (5) the precipitate obtained in the step (4) was dried at 80 C. overnight, then ground to obtain a NiCoZn alloy magnesium-aluminum spinel catalyst precursor; and [0040] (6) the NiCoZn alloy magnesium-aluminum spinel catalyst precursor was placed in a tubular furnace of a 10% H.sub.2 and 90% N.sub.2 atmosphere at a heating rate of 2 C./min, heated up to 600 C. and kept for 2 h, and cooled with the furnace to room temperature to obtain a catalyst NiCoZn/MgAlO.sub.x.

[0041] As shown in FIG. 1, hot electron injection induced by the localized surface plasmon resonance (LSPR) of the catalyst NiCoZn/MgAlO.sub.x activated a first CH bond of CH.sub.4 and a CO bond of CO.sub.2, further inducing the reaction. As shown in FIG. 2, nano-scale bright spots were NiCoZn metallic particle, with a particle size of approximately 18.5 nm. Combining with an XRD spectrum of the catalyst in FIG. 3, a catalyst carrier was magnesium-aluminum spinel, indicating that the prepared catalyst was the nickel-cobalt-zinc alloy catalyst (NiCoZn/MgAlO.sub.x), and had an amorphous structure.

Example 2

[0042] A preparation method for a plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst, which is specifically prepared by the following method: [0043] (1) 0.582 g of nickel nitrate hexahydrate, 0.582 g of cobalt nitrate hexahydrate, 2.39 g of zinc nitrate hexahydrate, 1.023 g of magnesium nitrate hexahydrate, and 7.5 g of aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water, and stirred with a magnetic stirrer at room temperature for 30 min to form a first solution; [0044] (2) 50 mL of 1.83 mol/L sodium hydroxide solution was added to the mixed solution obtained in the step (1), then sonicated and stirred vigorously for 4 h; [0045] (3) the stirred solution in the step (2) was transferred into a PTEE-lined container, which was then placed in a high-pressure reactor to react at 130 C. for 48 h; [0046] (4) the mixed solution obtained after hydrothermal treatment in the step (3) was centrifuged at 6000 r/min to obtain a precipitate, the precipitate was then washed five times with water and ethanol; [0047] (5) the precipitate obtained in the step (4) was dried at 80 C. overnight, then ground to obtain a NiCoZn alloy magnesium-aluminum spinel catalyst precursor; and [0048] (6) the NiCoZn alloy magnesium-aluminum spinel catalyst precursor was placed in a tubular furnace of a 10% H.sub.2 and 90% N.sub.2 atmosphere at a heating rate of 2 C./min, heated up to 600 C. and kept for 2 h, and cooled with the furnace to room temperature to obtain a catalyst NiCoZn.sub.2/MgAlO.sub.x.

Comparative Example 1

[0049] A preparation method for a plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst, which is specifically prepared by the following method: [0050] (1) 0.582 g of nickel nitrate hexahydrate, 0.582 g of cobalt nitrate hexahydrate, 1.19 g of copper nitrate hexahydrate, 1.023 g of magnesium nitrate hexahydrate, and 7.5 g of aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water, and stirred with a magnetic stirrer at room temperature for 30 min to form a first solution; [0051] (2) 50 mL of 1.68 mol/L sodium hydroxide solution was added to the mixed solution obtained in the step (1), then sonicated and stirred vigorously for 4 h; [0052] (3) the stirred solution in the step (2) was transferred into a polytetrafluoroethylene (PTEE)-lined container, which was then placed in a high-pressure reactor to react at 130 C. for 48 h; [0053] (4) the mixed solution obtained after hydrothermal treatment in the step (3) was centrifuged at 6000 r/min to obtain a precipitate, the precipitate was then washed five times with water and ethanol; [0054] (5) the precipitate obtained in the step (4) was dried at 80 C. overnight, then ground to obtain a NiCoCu magnesium-aluminum spinel catalyst precursor; and [0055] (6) the NiCoCu magnesium-aluminum spinel catalyst precursor was placed in a tubular furnace of a 10% H.sub.2 and 90% N.sub.2 atmosphere at a heating rate of 2 C./min, heated up to 600 C. and kept for 2 h, and cooled with the furnace to room temperature to obtain a catalyst NiCoCu/MgAlO.sub.x.

Comparative Example 2

[0056] A preparation method for a plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst, which is specifically prepared by the following method: [0057] (1) 1.164 g of nickel nitrate hexahydrate, 1.023 g of magnesium nitrate hexahydrate, and 7.5 g of aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water, and stirred with a magnetic stirrer at room temperature for 30 min to form a first solution; [0058] (2) 50 mL of 1.68 mol/L sodium hydroxide solution was added to the mixed solution obtained in the step (1), then sonicated and stirred vigorously for 4 h; [0059] (3) the stirred solution in the step (2) was transferred into a polytetrafluoroethylene (PTEE)-lined container, which was then placed in a high-pressure reactor to react at 130 C. for 48 h; [0060] (4) the mixed solution obtained after hydrothermal treatment in the step (3) was centrifuged at 6000 r/min to obtain a precipitate, the precipitate was then washed five times with water and ethanol; [0061] (5) the precipitate obtained in the step (4) was dried at 80 C. overnight, then ground to obtain a Ni/Mg aluminum spinel catalyst precursor; and [0062] (6) the Ni/Mg aluminum spinel catalyst precursor was placed in a tubular furnace of a 10% H.sub.2 and 90% N.sub.2 atmosphere at a heating rate of 2 C./min, heated up to 600 C. and kept for 2 h, and cooled with the furnace to room temperature to obtain a catalyst Ni/MgAlO.sub.x.

Comparative Example 3

[0063] A preparation method for a plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst, which is specifically prepared by the following method: [0064] (1) 1.164 g of cobalt nitrate hexahydrate, 1.023 g of magnesium nitrate hexahydrate, and 7.5 g of aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water, and stirred with a magnetic stirrer at room temperature for 30 min to form a first solution; [0065] (2) 50 mL of 1.68 mol/L sodium hydroxide solution was added to the mixed solution obtained in the step (1), then sonicated and stirred vigorously for 4 h; [0066] (3) the stirred solution in the step (2) was transferred into a polytetrafluoroethylene (PTEE)-lined container, which was then placed in a high-pressure reactor to react at 130 C. for 48 h; [0067] (4) the mixed solution obtained after hydrothermal treatment in the step (3) was centrifuged at 6000 r/min to obtain a precipitate, the precipitate was then washed five times with water and ethanol; [0068] (5) the precipitate obtained in the step (4) was dried at 80 C. overnight, then ground to obtain a Co/Mg aluminum spinel catalyst precursor; and [0069] (6) the Co/Mg aluminum spinel catalyst precursor was placed in a tubular furnace of a 10% H.sub.2 and 90% N.sub.2 atmosphere at a heating rate of 2 C./min, heated up to 600 C. and kept for 2 h, and cooled with the furnace to room temperature to obtain a catalyst Co/MgAlO.sub.x.

Comparative Example 4

[0070] A preparation method for a plasmonic nano-alloy photothermal-coupled methane dry reforming catalyst, which is specifically prepared by the following method: [0071] (1) 0.582 g of nickel nitrate hexahydrate, 0.582 g of cobalt nitrate hexahydrate, 1.023 g of magnesium nitrate hexahydrate, and 7.5 g of aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water, and stirred with a magnetic stirrer at room temperature for 30 min to form a first solution; [0072] (2) 50 mL of 1.68 mol/L sodium hydroxide solution was added to the mixed solution obtained in the step (1), then sonicated and stirred vigorously for 4 h; [0073] (3) the stirred solution in the step (2) was transferred into a polytetrafluoroethylene (PTEE)-lined container, which was then placed in a high-pressure reactor to react at 130 C. for 48 h; [0074] (4) the mixed solution obtained after hydrothermal treatment in the step (3) was centrifuged at 6000 r/min to obtain a precipitate, the precipitate was then washed five times with water and ethanol; [0075] (5) the precipitate obtained in the step (4) was dried at 80 C. overnight, then ground to obtain a NiCo alloy aluminum spinel catalyst precursor; and [0076] (6) the NiCo alloy aluminum spinel catalyst precursor was placed in a tubular furnace of a 10% H.sub.2 and 90% N.sub.2 atmosphere at a heating rate of 2 C./min, heated up to 600 C. and kept for 2 h, and cooled with the furnace to room temperature to obtain a catalyst NiCo/MgAlO.sub.x.

[0077] Photothermal-driven methane dry reforming for hydrogen production was performed in a photothermal reactor, and the catalyst was placed in a special reaction crucible. During the reaction, a mixed gas of methane, carbon dioxide and nitrogen was continuously introduced into a pipeline, a xenon lamp was then turned on to irradiate a surface of the catalyst with ultraviolet-visible light, in which case, the catalyst absorbed high-energy photons to reach a reaction temperature for photothermal-coupled methane dry reforming to produce hydrogen.

[0078] An activity test of the catalyst for photothermal-driven methane dry reforming to produce hydrogen was, and the test includes the following steps: [0079] (1) 0.014 g of catalyst was weighed and placed into a reaction crucible; [0080] (2) a mixed gas of methane, carbon dioxide and nitrogen was continuously introduced into a pipeline of the reactor to purge the air in the pipeline; [0081] (3) a volume ratio of methane, carbon dioxide, and nitrogen before being introduced into the reactor was 41.8%/43.2%/17.8%, and a total flow rate of the mixed gas was 101 ml/min; [0082] (4) a xenon lamp was turned on to irradiate with ultraviolet-visible light, sunlight was simulated for focused lighting, with a light intensity of 11.6 W, a light spot size of 6 mm, directly irradiating a surface of the catalyst Ni/MgAlO.sub.x; [0083] (5) after absorbing high-energy photons, the Ni/MgAlO.sub.x catalyst rapidly heated up to a required reaction temperature; [0084] (6) photothermal-coupled methane dry reforming was carried out to produce hydrogen; and [0085] (7) a reaction gas was introduced into a gas chromatograph for analysis; a yield of H.sub.2 was 118.2 mmol/min/g.sub.cat, and a yield of CO was 128.4 mmol/min/g.sub.cat.

[0086] Gas chromatograph detection and subsequent calculations indicated that the catalyst used in Example 1 for photothermal-coupled methane dry reforming for hydrogen production had a yield of H.sub.2 up to 173.6 mmol/min/g.sub.cat and a yield of CO up to 178.6 mmol/min/g.sub.cat. The catalyst used in Comparative Example 3 for photothermal-coupled methane dry reforming for hydrogen production had a yield of H.sub.2 up to 94 mmol/min/g.sub.cat and a yield of CO up to 108 mmol/min/g.sub.cat.

[0087] As shown in FIGS. 4-5, the Ni, Co, and Zn loadings in the catalyst prepared in Example 1 were 6.7%, 7.3%, and 0.87%, respectively, the synthesized catalyst NiCoZn/MgAlO.sub.x exhibited great advantages in terms of reaction gas conversion rate, carbon deposition resistance, hydrogen-carbon monoxide ratio, solar-to-fuel efficiency, and the like when a molar ratio of Mg:Al was 1:5. The catalyst also had excellent stability during the reaction (FIG. 6). In addition, as shown in FIGS. 7-8, the catalyst had strong light absorption capabilities, particularly in a visible light range of 450 nm, offering excellent light absorption and catalytic performance, which was attributed to hot electrons generated by the plasmonic effect of the catalyst NiCoZn/MgAlO.sub.x under lighting at the wavelength, promoting the dry reforming reaction, and providing theoretical guidance for future photothermal coupling experiments.

[0088] As shown in FIG. 9, DFT calculations indicated that the NiCoZn ternary alloy had significant advantages in the main reactions of methane dry reforming, effectively activated the reactant molecules CH.sub.4 and CO.sub.2, had lower activation energy for breaking the CH bond, and exhibited higher activation energy in a final step of CH.sub.4 cleavage, which could inhibit the carbon deposition caused by methane cracking and promote the orderly steps of the reaction to CH oxidation. In addition, as shown in FIG. 10, the catalytic results of the same ternary nano-alloy catalyst indicated that the light-fuel conversion efficiency of NiCoZn/MgAlO.sub.xwas significantly higher than that of NiCoCu/MgAlO.sub.x, proving that the addition of Zn greatly had great advantages in the catalytic performance of the catalyst for methane dry reforming.